Hiroko Kakuda

Efficient synthesis of (R)- and (S)-1-amino-2,2-difluorocyclopropanecarboxylic acid via lipase-catalyzed desymmetrization of prochiral precursors

The asymmetric syntheses of (+)-(R)-1-amino-2,2-difluorocyclopropane-1-carboxylic acid and its enantiomer have been accomplished. Key reactions in the synthetic design are lipase-catalyzed desymmetrization of a prochiral diol and a prochiral diacetate.

Efficient fragmentation of the tertiary cyclopropanol system: Oxidation of 1-(trimethylsiloxy)bicyclo[n.1.0]alkanes and analogues by using phenyliodine(III) diacetate

Abstract Oxidation of 1-(trimethylsiloxy)bicyclo[n.1.0]alkanes and analogues with phenyliodine(III) diacetate (PIDA) in acetic acid caused fragmentation to give alkenoic acids in high yields.

Asymmetric synthesis of 2-substituted chroman-4-ones using lipase-catalyzed kinetic resolutions

2-Methylchroman-4-one and 2-phenylchroman-4-one were synthesized in optically active form. Their chiral intermediates were obtained via lipase-catalyzed enantioselective reactions.

Model studies toward the total synthesis of halenaquinol and halenaquinone

A strategy for the synthesis of the furan-fused tetracyclic core of halenaquinol and halenaquinone was explored through a model study. The synthesis involved the intramolecular [4+2] cycloaddition reaction of the o-quinodimethane, generated from benzocyclobutene as the key step.

Hypervalent λn-iodane-mediated fragmentation of tertiary cyclopropanol systems

Abstract The oxidation of tertiary cyclopropyl silyl ethers with hypervalent λn-iodanes caused fragmentation which produced alkenoic acids or esters.

Hypervalent λn-iodane-mediated fragmentation of tertiary cyclopropanol systems II: Application to asymmetric syntheses of piperidine and indolizidine alkaloids

Abstract The asymmetric synthesis of (−)-pinidine and its enantiomer was accomplished by starting from norgranatanone via the asymmetric enolization, stereoselective cyclopropanation, and oxidative ring cleavage of the resulting cyclopropanol system with a hypervalent λ n -iodane as key steps. Formal asymmetric synthesis of (+)-indolizidine 223AB was also performed via the asymmetric enolization and oxidative ring cleavage of the resulting cyclopropanol system as key steps.

Synthesis of optically active 2,2-difluorohomoallylalcohols by lipase-catalyzed transesterification

Abstract Racemic 2,2-difluorohomoallylalcohols could be resolved into ( R )-alcohols and ( S )-acetates through Pseudomonas fluorescens lipase-catalyzed enantioselective transesterification. The utility of the resulting chiral, non-racemic 2,2-difluorohomoallylalcohols was demonstrated by conversion of one of the ( S )-acetates into a synthetically important 2,2-difluoro-3-hydroxycarboxylate derivative.

8α-hydroxy-11α,13-dihydrozaluzanin C

In the structure of the title compound [3a,4,5,6,6a,7,8,9,-9a,9b-decahydro-4,8-dihydroxy-3-methyl-6,9-bis(methyl-ene)azuleno[4,5-b]furan-2(3H)-one, C 15 H 20 O 4 ], the secondary hydroxyl groups participate in intermolecular hydrogen bonds both as donors and acceptors.

(1Z,2Z)-1,2-Bis(3-methyl-2,3-dihydro-1,3-benzothiazol-2-ylidene)hydrazine

The title compound, C16H14N4S2, crystallizes in symmetry group C2. The molecule is planar with C2h symmetry, with the inversion centre at the mid-point of the hydrazine N-N bond, and it has an N-N s-trans conformation and a Z,Z configuration. The particular crystal examined was a racemic twin, as suggested by the Flack parameter of 0.41 (2) [Flack (1983). Acta Cryst. A39, 876-881].

(2S)-2-[(1R)-1-Iodo­ethyl]-1-(4-methyl­phen­ylsulfon­yl)pyrrolidine

The spectroscopically confused title compound, C13H18INO2S, wrongly assigned previously, has been crystallographically identified. The relative configuration is the (R*,S*) form and not the (R*,R*) type as previously reported.